﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ljc01
{
    class Program
    {
        static void Main(string[] args)
        {
            double r;
            double area;
            Console.WriteLine("请输入圆的半径：");
            r = double.Parse(System.Console.ReadLine());
            area = 3.14*(r*r);
            Console.WriteLine("圆的面积为" + area);
            Console.ReadKey();

        }
    }
}
